title: Responsiveness and minimally important difference for the patient-reported outcomes measurement information system (PROMIS) 20-item physical functioning short form in a prospective observational study of rheumatoid arthritis.
abstract: OBJECTIVE
  To estimate responsiveness (sensitivity to change) and minimally important difference (MID) for the Patient-Reported Outcomes Measurement Information System (PROMIS) 20-item physical functioning scale (PROMIS PF-20).
  
  
  METHODS
  The PROMIS PF-20, short form 36 (SF-36) physical functioning scale, and Health Assessment Questionnaire (HAQ) were administered at baseline, and 6 and 12 months later to a sample of 451 persons with rheumatoid arthritis. A retrospective change (anchor) item was administered at the 12-month follow-up. We estimated responsiveness between 12 months and baseline, and between 12 months and 6 months using one-way analysis of variance F-statistics. We estimated the MID for the PROMIS PF-20 using prospective change for people reporting getting 'a little better' or 'a little worse' on the anchor item.
  
  
  RESULTS
  F-statistics for prospective change on the PROMIS PF-20, SF-36 and HAQ by the anchor item over 12 and 6 months (in parentheses) were 16.64 (14.98), 12.20 (7.92) and 10.36 (12.90), respectively. The MID for the PROMIS PF-20 was 2 points (about 0.20 of an SD).
  
  
  CONCLUSIONS
  The PROMIS PF-20 is more responsive than two widely used ('legacy') measures. The MID is a small effect size. The measure can be useful for assessing physical functioning in clinical trials and observational studies.
authors.affiliation: Department of Medicine, UCLA Division of General Internal Medicine & Health Services Research, Los Angeles, California, USA RAND, Santa Monica, California, USA.
authors.forename: Ron D
authors.initials: RD
authors.lastname: Hays
authors.affiliation: Department of Medicine, UCLA Division of General Internal Medicine & Health Services Research, Los Angeles, California, USA.
authors.forename: Karen L
authors.initials: KL
authors.lastname: Spritzer
authors.affiliation: Stanford ARAMIS Program, Stanford University School of Medicine, Palo Alto, California, USA.
authors.forename: James F
authors.initials: JF
authors.lastname: Fries
authors.affiliation: Stanford ARAMIS Program, Stanford University School of Medicine, Palo Alto, California, USA.
authors.forename: Eswar
authors.initials: E
authors.lastname: Krishnan
mesh_terms: D000203:Activities of Daily Living; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000503:physiopathology* / Q000628:therapy; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D063868:Patient Outcome Assessment; D011446:Prospective Studies; D015203:Reproducibility of Results; D057566:Self Report; D011795:Surveys and Questionnaires
keywords: Health Services Research; Outcomes Research; Rheumatoid Arthritis